GB2274343A - Waste water pump motor electronic control circuit - Google Patents

Abstract

An Electronic Control Circuit, which is fitted in series with the waste water pump motor circuit of domestic Automatic Condenser Washer Dryer appliances or domestic Automatic Washing Machine appliances for the purposes of reducing noise emissions and improving electrical energy efficiency and pump motor life, senses when there is no more water in the appliance tub to be pumped and then switches the waste pump motor off for a timed period to allow more water to accumulate in the tub. At the end of this timed period the waste pump motor is automatically restarted. The Control Circuit also incorporates a waste pump to filling solenoids interlock relay to prevent any possibility of the appliance filling at the wrong time and/or filling and emptying simultaneously. <IMAGE>

Description

WASTE WATER PUMP MOTOR ELECTRONIC CONTROL CIRCUIT This invention relates to an Electronic Control Circuit to be fitted to domestic laundry Automatic Condenser Washer Dryer appliances and domestic laundry Automatic Washing Machine appliances.

Automatic Condenser Washer Dryers are well known domestic appliances that can function as Automatic Washing Machines and Tumble Dryers for laundry.

In the drying mode they also have the added advantage over conventional Tumble Dryers of not requiring an air vent pipe to dispose of moisture laden air.

The Automatic Washing Machine section of the Washer Dryer is basically identical to conventional Automatic Washing Machines and does not warrant further description here. In the drying mode however, the inside of the tub becomes part of an enclosed circuit, around which, heated air is circulated, absorbing water vapour as it passes through the tumbling laundry. As the hot air leaves the tub it enters a chamber or duct where a jet of cold water from the mains supply is spraying, and in doing so condenses any water vapour present. This condensate along with the spray water itself then falls to the waste pump section of the appliance where it is pumped away to the household drains. The dried air continues around the enclosed circuit, past the circulating fan and the heating elements, and then into the tub once more and begins the cycle over again.

This process normally takes up to two hours to thoroughly dry the maximum drying load of laundry, and during this time, the waste water pump is continually running to dispose of the spray and condensate water, otherwise, the tub would slowly fill up, resoaking the laundry, and even worse, blocking off the hot air circuit and leading to overheating of the heating elements and the possible outbreak of fire. Flooding might also eventually occur. It is therefore fundamental to the process that the spray water is disposed of in a safe and reliable manner.

Now although the continual running of the waste water pump allows the Dryer to function correctly, it is very noisy and inefficient in practice.

It is very noisy because the waste pump itself is designed to pump a lot of water at a very fast rate to enable it to cope with the demands of the washing mode, but here in the drying mode, it is presented with only a small trickle of water from the condensate spray and the impeller is effectively spinning in air and merely surging a column of air and water up and down the drain hose producing loud noise emissions. On a busy washday with multiple drying loads this could mean a consumers kitchen environment sustaining high noise levels for up to eight hours just to dry two large washing loads. (one full washing load equals approximately two full drying loads of two hours duration each) A state of affairs that could be improved.It is also energy inefficient because the pump motor is running with no load for very long periods and in addition is wearing the motor out at a considerable rate.

Although a conventional Automatic Washing Machine does not run it's waste pump empty for the lengthy periods of the Washer Dryer, they often do so for several minutes on certain programme steps and so can create the same loud noise emissions as the Washer Dryer, albeit for much shorter periods.

They do therefore, also have some room for improvement in this area.

Noise emissions, energy efficiency and pump motor life could be dramatically improved if the pump only runs when there is an adequate build up of water in the tub, and cuts out again at the instant the water is gone.

The first of those requirements - to allow a build up of water prior to disposal, necessitates a precise and reliable method of control over the maximum level the water is allowed to reach. It must not be allowed to become so high that it enters the drum and resoaks the laundry, or even worse, blocks of the hot air circulation aperture in the tub wall.

Fortunately, the rate of water ingression from the condensing spray is a steady one and can be plotted against time to enable accurate control of the maximum tub water level. By the time the water reaches it's maximum allowed level the waste pump MUST be AUTOMATICALLY restarted.

The second requirement - for the pump to cut out at the instant the water has gone i.e. "The Tub Empty Point", can be met by monitoring the electrical current of the pump motor, and using the point at which air reaches the pump impeller and changes the motor current, as an electrical trigger signal to switch the pump off.

Several additional requirements also have to be met, one of which is for the waste pump motor to always start when it's power supply is first initiated by the appliance's programmer. This is to enable any prior accumulations of water (from any source) to be disposed of immediately and to fit in with the requirements of the washing, rinsing and spinning modes without any undue delay.

Another requirement is that any interlock system between the appliance's waste pump circuit and the appliance's filling solenoids (to prevent the machine filling and emptying at the same time) is properly catered for.

Last but not least the control circuit must function reliably with a high level of mains borne interference, especially with regard to that emanating from the switching circuits of the appliance 5 drum motor.

The following example of this invention fulfills these requirements well and is adjusted for a timed delay period of forty five seconds. In practice the waste pump runs for approximately five seconds out of every fifty seconds and the pump noise emissions are a very small fraction of those previously, in fact being completely silent for forty five seconds out of every fifty and significantly reduced for the other five.

According to the present invention there is provided an Electronic Control Circuit to be fitted in series with the waste water pump motor circuit of domestic laundry Automatic Condenser Washer Dryer appliances and domestic laundry Automatic Washing Machine appliances, whereby the waste water pump motor is switched off for a timed period at the instant the tub becomes empty of water.

A specific embodiment of the invention will now be described by way of example, with reference to the accompanying drawings in which Drawing Sheet No. 1 - is a Block Diagram showing the various sections of the Electronic Control Circuit and their interelation with the appropriate sections of the Washer Dryer appliance or Washing Machine appliance.

Drawing Sheet No. 2 - is a Schematic Diagram of the Electronic Control Circuit showing the electrical and electronic components and their interconnections.

Referring to the Block Diagram of drawing sheet No. 1, it is shown simply how the five basic sections of the Control Circuit interelate with the Appliance Programmer, Appliance Waste Pump Motor and the Appliance Filling Solenoids.

With regard to the Schematic Diagram of drawing sheet No. 2, it can be seen that the Control Circuit is in series with the Appliance Programmer Waste Pump Switch (APS) and that consequently the Appliance Programmer still retains overall control of the waste pump programming.

The miniature relay REL.2 is energised by the Control Circuit power supply rail coming from the LM7808CT voltage regulator (I.C.1) and performs the function of the Interlock between the waste pump motor and the appliance filling solenoids. This prevents any possibility of the Appliance filling when the Triac is off, or additionally, at any time when the waste pump circuit is energised by the Appliance Programmer Switch (APS).

Suppression of voltage surges and interference is provided by Varistor 1 (VAR.1) and Varistor 2 (VAR.2) and the decoupling capacitors C3D, C6D, C7D and C9D.

Still referring to the schematic diagram of drawing sheet No. 2 it can be seen that a power factor correction capacitor (C12) is fitted in parallel with the waste pump motor. This is to improve the modulation of the supply current by the pump load. A signal voltage generating resistor (R20) is connected in series with the pump motor and the signal voltage produced is coupled into the signal conditioning rectifier (RECT 2) via -the mains isolating transformer (TX2). From the rectifier the signal passes through the signal conditioning circuitry to the trigger take-off point between R14 and C9. From this single point two simple potential divider circuits are taken to the negative rail.The middle of one being capacitively loaded or damped to the negative rail by C7 and the middle of the other being capacitively driven or modulated by C8 from the trigger take-off point between R14 and C9. An LM311N Comparator integrated circuit (I.C.3) is used to monitor the voltage difference between the middle points of these potential dividers.

When the pump motor current and consequently the signal voltage, is stable or increasing, the potential divider being driven by C8 has a slightly higher voltage (as seen by the comparator) than the potential divider being loaded by C7, and the reed relay (REL.1) is not activated by the comparator. But when the signal decreases rapidly, as when the pump runs out of water, the capacitively driven potential divider reacts faster than the capacitively loaded potential divider and momentarily swings negative to it as seen by the comparator, which then momentarily activates the reed relay (REL.1). This in turn triggers the ZN1034 precision timer (I.C.2) into the timing state, switching off the MOC3041 opto-isolator triac driver (I.C.4) and the Triac as it does so, and the pump motor is switched off. The precision timer (I.C.2) remains in this state for the timing period (in this case forty five seconds) and then AUTOMATICALLY reverts to it's pre-triggered state, switching it's output back again as it does so and reactivating the triac driver (I.C.4) and the Triac.

Consequently the pump motor is switched on again.

It should be noted that adjustment of the triggering sensitivity is provided for by the potentiometer (POT 1).

Claims (1)

1. CLAIM 1 An Electronic Control Circuit to be fitted in series with the waste water pump motor circuit of domestic laundry Automatic Condenser Washer Dryer appliances and domestic laundry Automatic Washing Machine appliances, whereby the waste water pump motor is switched off for a timed period when the appliance tub becomes empty of water.

   CLAIM 2 An Electronic Control Circuit as in Claim 1 wherein the "Tub Empty Point" is detected by the change in the waste water pump motor current when the pump impeller starts spinning in air instead of water. This change in motor current being utilised as a Trigger Signal.

   CLAIM 3 An Electronic Control Circuit as in Claims 1 & 2 wherein the Trigger Signal is a function of rapid signal change and not signal level itself, i.e. a falling waveform.

   CLAIM 4 An Electronic Control Circuit as in Claims 1,2, & 3 wherein the signal derived from the waste pump motor current is coupled into the signal conditioning circuitry by means of an isolating transformer.

   CLAIM 5 An Electronic Control Circuit as in Claims 1,2,3 & 4 wherein a timer is used to determine the end of a delay period that commenced at the "Tub Empty Point" after which period the waste water pump motor is automatically restarted.

   CLAIM 6 An Electronic Control Circuit as in Claims 1,2,3,4 & 5 wherein the timer contains an oscillator and multi-stage divider counting circuit.

   CLAIM 7 An Electronic Control Circuit as in Claims 1,2,3,4,5 & 6 wherein a filling solenoids to waste pump motor interlock relay, activated by the energising of the power supply rail of the aforementioned circuit, or directly activated by the appliance's waste water pump motor switching circuit, interupts the power supply to the appliance's water filling solenoids.